Impact of position sensor accuracy on the performance of propulsion IPM drives

This paper addresses the influence of rotor position sensor accuracy on the performance of the Interior Permanent Magnet (IPM) motor drives used for automotive propulsion application. Analytical equations for the torque production in IPM machines show that the machine output torque drops sharply with angle error at high operating speeds. This also shows the need for rotor position feedback with high accuracy and resolution, especially for operation in the flux weakening region. Finite element analysis was performed to substantiate this conclusion and also to estimate the torque and power degradation due to the position sensor error. The torque/speed curves on an experimental drive system was measured on the dyno to corroborate the analytical and simulation results. The dynamic angle error of a typical high resolution/accuracy sensor was measured on the test bench at various operating speeds and temperatures and the measured data was used for computing the impact of angle error on the torque ripple. The details of these results are presented in the paper.